| Oracle® Spatial User's Guide and Reference 10g Release 1 (10.1) Part Number B10826-01 |
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| Oracle® Spatial User's Guide and Reference 10g Release 1 (10.1) Part Number B10826-01 |
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View PDF |
This chapter describes the SQL statements used when working with the spatial object data type. The statements are listed in Table 10-1.
Table 10-1 Spatial Index Creation and Usage Statements
| Statement | Description |
|---|---|
| ALTER INDEX |
Alters specific parameters for a spatial index. |
| ALTER INDEX REBUILD |
Rebuilds a spatial index or a specified partition of a partitioned index. |
| ALTER INDEX RENAME TO |
Changes the name of a spatial index or a partition of a spatial index. |
| CREATE INDEX |
Creates a spatial index on a column of type SDO_GEOMETRY. |
| DROP INDEX |
Deletes a spatial index. |
This chapter focuses on using these SQL statements with spatial indexes. For complete reference information about any statement, see Oracle Database SQL Reference.
Bold italic text is often used in the Keywords and Parameters sections in this chapter to identify a grouping of keywords, followed by specific keywords in the group. For example, INDEX_PARAMS identifies the start of a group of index-related keywords.
Purpose
Alters specific parameters for a spatial index.
Syntax
ALTER INDEX [schema.]index PARAMETERS ('index_params [physical_storage_params]' )
[{ NOPARALLEL | PARALLEL [ integer ] }] ;
Keywords and Parameters
| Value | Description |
|---|---|
| INDEX_PARAMS | Allows you to change the characteristics of the spatial index. |
| index_status | Specifies that index modifications are to be deferred ('index_status=deferred') or that deferred index modifications are to be synchronized with the data in the spatial table ('index_status=synchronize'). See the Usage Notes for further details.Data type is VARCHAR2. |
| sdo_batch_size | Specifies the number of rows to be processed at a time when the index is synchronized ('index_status=synchronize'). See Section 4.1.3 for more information about using this keyword to improve performance when many rows need to be inserted.Data type is NUMBER. For example: 'sdo_batch_size=500' |
| sdo_indx_dims | Specifies the number of dimensions to be indexed. For example, a value of 2 causes the first two dimensions to be indexed. Must be less than or equal to the number of actual dimensions (number of SDO_DIM_ELEMENT instances in the dimensional array that describes the geometry objects in the column). If the value is 3 or higher, the only Spatial operator that can be used on the indexed geometries is SDO_FILTER; the other operators described in Chapter 12 cannot be used. Data type is NUMBER. Default = 2. |
| sdo_rtr_pctfree | Specifies the minimum percentage of slots in each index tree node to be left empty when the index is created. Slots that are left empty can be filled later when new data is inserted into the table. The value can range from 0 to 50. The default value is best for most applications; however, a value of 0 is recommended if no updates will be performed to the geometry column. Data type is NUMBER. Default = 10. |
| PHYSICAL_STORAGE_PARAMS | Determines the storage parameters used for altering the spatial index data table. A spatial index data table is a standard Oracle table with a prescribed format. Not all physical storage parameters that are allowed in the STORAGE clause of a CREATE TABLE statement are supported. The following is a list of the supported subset. |
| tablespace | Specifies the tablespace in which the index data table is created. This parameter is the same as TABLESPACE in the STORAGE clause of a CREATE TABLE statement. |
| initial | Is the same as INITIAL in the STORAGE clause of a CREATE TABLE statement. |
| next | Is the same as NEXT in the STORAGE clause of a CREATE TABLE statement. |
| minextents | Is the same as MINEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| maxextents | Is the same as MAXEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| pctincrease | Is the same as PCTINCREASE in the STORAGE clause of a CREATE TABLE statement. |
| { NOPARALLEL | PARALLEL [ integer ] } | Controls whether serial execution (NOPARALLEL) or parallel (PARALLEL) execution is used for subsequent queries and DML operations that use the index. For parallel execution you can specify an integer value of degree of parallelism. See the Usage Notes for the CREATE INDEX statement for guidelines and restrictions that apply to the use of the PARALLEL keyword. Default = NOPARALLEL. (If PARALLEL is specified without an integer value, the Oracle database calculates the optimum degree of parallelism.) |
Prerequisites
You must have EXECUTE privileges on the index type and its implementation type.
The spatial index to be altered is not marked in-progress.
Usage Notes
This statement is used to change the parameters of an existing index. This is the only way you can add or build multiple indexes on the same column.
The index_status keyword lets you defer modifications to the spatial index when geometries are inserted, updated, or deleted in a spatial table. Deferring the index modifications allows the geometry insert, update, and delete operations to be completed sooner, and it can reduce concurrency issues with R-tree indexes if multiple sessions are inserting rows into the spatial table. While index modifications are being deferred, spatial functions and procedures will work correctly with the current table data; however, spatial operator-based queries might perform more slowly, will not include the results of new insert operations, and might not include the results of new update operations. Therefore, you are advised not to use spatial operators while index modifications are being deferred.
For partitioned indexes, the index status can only be changed for a single partition at a time. That is, you cannot set all index partitions to deferred status with a single ALTER INDEX statement.
If you set the index status to deferred, you must later specify index_status=synchronize to make the index reflect the data in the table and to set the index to a valid state. Another use of index_status=synchronize is to return the index to a consistent state if an attempt to commit or roll back a transaction failed due to insufficient resources.
See the Usage Notes for the CREATE INDEX statement for usage information about many of the other available parameters.
Examples
The following example modifies the tablespace and the SDO_LEVEL value for partition IP2 of the spatial index named BGI.
ALTER INDEX bgi MODIFY PARTITION ip2
PARAMETERS ('tablespace=TBS_3 sdo_level=4');
The following example defers index modifications and later (after the updates to the spatial table) synchronizes the index to reflect the table.
ALTER INDEX xyz_idx PARAMETERS ('index_status=deferred');
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. <Insert rows in spatial table.>
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ALTER INDEX xyz_idx PARAMETERS ('index_status=synchronize');
The following example defers index modifications for an index partition and later (after the updates to the spatial table) synchronizes the index partition to reflect the table.
ALTER INDEX part_sidx MODIFY PARTITION p3
PARAMETERS ('index_status=deferred');
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. <Insert rows in spatial table.>
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ALTER INDEX part_sidx MODIFY PARTITION p3
PARAMETERS ('index_status=synchronize');
Related Topics
ALTER TABLE (clauses for partition maintenance) in Oracle Database SQL Reference
Syntax
ALTER INDEX [schema.]index REBUILD
[PARAMETERS ('rebuild_params [physical_storage_params]' ) ]
[{ NOPARALLEL | PARALLEL [ integer ] }] ;
ALTER INDEX [schema.]index REBUILD PARTITION partition
[PARAMETERS ('rebuild_params [physical_storage_params]' ) ] ;
Purpose
Rebuilds a spatial index or a specified partition of a partitioned index.
Keywords and Parameters
| Value | Description |
|---|---|
| REBUILD_PARAMS | Specifies in a command string the index parameters to use in rebuilding the spatial index. |
| layer_gtype | Checks to ensure that all geometries are of a specified geometry type. The value must be from the Geometry Type column of Table 2-1 in Section 2.2.1 (except that UNKNOWN_GEOMETRY is not allowed). In addition, specifying POINT allows for optimized processing of point data. Data type is VARCHAR2. |
| rebuild_index | Specifies the name of the spatial index table to be rebuilt. Data type is VARCHAR2. |
| sdo_indx_dims | Specifies the number of dimensions to be indexed. For example, a value of 2 causes the first two dimensions to be indexed. Must be less than or equal to the number of actual dimensions (number of SDO_DIM_ELEMENT instances in the dimensional array that describes the geometry objects in the column). If the value is 3 or higher, the only Spatial operator that can be used on the indexed geometries is SDO_FILTER; the other operators described in Chapter 12 cannot be used. Data type is NUMBER. Default = 2. |
| sdo_rtr_pctfree | Specifies the minimum percentage of slots in each index tree node to be left empty when the index is created. Slots that are left empty can be filled later when new data is inserted into the table. The value can range from 0 to 50. Data type is NUMBER. Default = 10. |
| PHYSICAL_STORAGE_PARAMS | Determines the storage parameters used for rebuilding the spatial index data table. A spatial index data table is a regular Oracle table with a prescribed format. Not all physical storage parameters that are allowed in the STORAGE clause of a CREATE TABLE statement are supported. The following is a list of the supported subset. |
| tablespace | Specifies the tablespace in which the index data table is created. Same as TABLESPACE in the STORAGE clause of a CREATE TABLE statement. |
| initial | Is the same as INITIAL in the STORAGE clause of a CREATE TABLE statement. |
| next | Is the same as NEXT in the STORAGE clause of a CREATE TABLE statement. |
| minextents | Is the same as MINEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| maxextents | Is the same as MAXEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| pctincrease | Is the same as PCTINCREASE in the STORAGE clause of a CREATE TABLE statement. |
| { NOPARALLEL | PARALLEL [ integer ] } | Controls whether serial execution (NOPARALLEL) or parallel (PARALLEL) execution is used for the rebuilding of the index and for subsequent queries and DML operations that use the index. For parallel execution you can specify an integer value of degree of parallelism. See the Usage Notes for the CREATE INDEX statement for guidelines and restrictions that apply to the use of the PARALLEL keyword. Default = NOPARALLEL. (If PARALLEL is specified without an integer value, the Oracle database calculates the optimum degree of parallelism.) |
Prerequisites
You must have EXECUTE privileges on the index type and its implementation type.
The spatial index to be altered is not marked in-progress.
Usage Notes
An ALTER INDEX REBUILD 'rebuild_params' statement rebuilds the index using supplied parameters. Spatial index creation involves creating and inserting index data, for each row in the underlying table column being spatially indexed, into a table with a prescribed format. All rows in the underlying table are processed before the insertion of index data is committed, and this requires adequate rollback segment space.
This statement does not use any previous parameters from the index creation. All parameters should be specified for the index you want to rebuild.
For more information about using the layer_gtype keyword to constrain data in a layer to a geometry type, see Section 4.1.4.
With a partitioned spatial index, you must use a separate ALTER INDEX REBUILD statement for each partition to be rebuilt.
See also the Usage Notes for the CREATE INDEX statement for usage information about many of the available parameters and about the use of the PARALLEL keyword.
Examples
The following example rebuilds OLDINDEX with an SDO_LEVEL value of 12.
ALTER INDEX oldindex REBUILD PARAMETERS('sdo_level=12');
Related Topics
ALTER TABLE and ALTER INDEX (clauses for partition maintenance) in Oracle Database SQL Reference
Syntax
ALTER INDEX [schema.]index RENAME TO <new_index_name>;
ALTER INDEX [schema.]index PARTITION partition RENAME TO <new_partition_name>;
Purpose
Changes the name of a spatial index or a partition of a spatial index.
Keywords and Parameters
| Value | Description |
|---|---|
| new_index_name | Specifies the new name of the index. |
| new_partition_name | Specifies the new name of the partition. |
Prerequisites
You must have EXECUTE privileges on the index type and its implementation type.
The spatial index to be altered is not marked in-progress.
Usage Notes
None.
Examples
The following example renames OLDINDEX to NEWINDEX.
ALTER INDEX oldindex RENAME TO newindex;
Related Topics
Syntax
CREATE INDEX [schema.]<index_name> ON [schema.]<tableName> (column)
INDEXTYPE IS MDSYS.SPATIAL_INDEX
[PARAMETERS ('index_params [physical_storage_params]' )]
[{ NOPARALLEL | PARALLEL [ integer ] }];
Purpose
Creates a spatial index on a column of type SDO_GEOMETRY.
Keywords and Parameters
| Value | Description |
|---|---|
| INDEX_PARAMS | Determines the characteristics of the spatial index. |
| geodetic | 'geodetic=FALSE' allows a non-geodetic index to be built on geodetic data, but with restrictions. (FALSE is the only acceptable value for this keyword.) See the Usage Notes for more information.Data type is VARCHAR2. |
| layer_gtype | Checks to ensure that all geometries are of a specified geometry type. The value must be from the Geometry Type column of Table 2-1 in Section 2.2.1 (except that UNKNOWN_GEOMETRY is not allowed). In addition, specifying POINT allows for optimized processing of point data. Data type is VARCHAR2. |
| sdo_indx_dims | Specifies the number of dimensions to be indexed. For example, a value of 2 causes the first two dimensions to be indexed. Must be less than or equal to the number of actual dimensions (number of SDO_DIM_ELEMENT instances in the dimensional array that describes the geometry objects in the column). If the value is 3 or higher, the only Spatial operator that can be used on the indexed geometries is SDO_FILTER; the other operators described in Chapter 12 cannot be used. Data type is NUMBER. Default = 2. |
| sdo_non_leaf_tbl | 'sdo_non_leaf_tbl=TRUE' creates a separate index table (with a name in the form MDNT_...$) for nonleaf nodes of the index, in addition to creating an index table (with a name in the form MDRT_...$) for leaf nodes. 'sdo_non_leaf_tbl=FALSE' creates a single table (with a name in the form MDRT_...$) for both leaf nodes and nonleaf nodes of the index. See the Usage Notes for more information.Data type is VARCHAR2. Default = FALSE |
| sdo_rtr_pctfree | Specifies the minimum percentage of slots in each index tree node to be left empty when the index is created. Slots that are left empty can be filled later when new data is inserted into the table. The value can range from 0 to 50. Data type is NUMBER. Default = 10. |
| PHYSICAL_STORAGE_PARAMS | Determines the storage parameters used for creating the spatial index data table. A spatial index data table is a regular Oracle table with a prescribed format. Not all physical_storage_params that are allowed in the STORAGE clause of a CREATE TABLE statement are supported. The following is a list of the supported subset. |
| tablespace | Specifies the tablespace in which the index data table is created. Same as TABLESPACE in the STORAGE clause of a CREATE TABLE statement. |
| initial | Is the same as INITIAL in the STORAGE clause of a CREATE TABLE statement. |
| next | Is the same as NEXT in the STORAGE clause of a CREATE TABLE statement. |
| minextents | Is the same as MINEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| maxextents | Is the same as MAXEXTENTS in the STORAGE clause of a CREATE TABLE statement. |
| pctincrease | Is the same as PCTINCREASE in the STORAGE clause of a CREATE TABLE statement. |
| work_tablespace | Specifies the tablespace for temporary tables used in creating the index. (Applies only to creating spatial R-tree indexes, and not to other types of indexes.) |
| { NOPARALLEL | PARALLEL [ integer ] } | Controls whether serial execution (NOPARALLEL) or parallel (PARALLEL) execution is used for the creation of the index and for subsequent queries and DML operations that use the index. For parallel execution you can specify an integer value of degree of parallelism. See the Usage Notes for more information about parallel index creation. Default = NOPARALLEL. (If PARALLEL is specified without an integer value, the Oracle database calculates the optimum degree of parallelism.) |
Prerequisites
All current SQL CREATE INDEX prerequisites apply.
You must have EXECUTE privilege on the index type and its implementation type.
The USER_SDO_GEOM_METADATA view must contain an entry with the dimensions and coordinate boundary information for the table column to be spatially indexed.
Usage Notes
For information about spatial indexes, see Section 1.7.
Before you create a spatial index, be sure that the rollback segment size and the SORT_AREA_SIZE parameter value are adequate, as described in Section 4.1.1.
If an R-tree index is used on linear referencing system (LRS) data and if the LRS data has four dimensions (three plus the M dimension), the sdo_indx_dims parameter must be used and must specify 3 (the number of dimensions minus one), to avoid the default sdo_indx_dims value of 2, which would index only the X and Y dimensions. For example, if the dimensions are X, Y, Z, and M, specify sdo_indx_dims=3 to index the X, Y, and Z dimensions, but not the measure (M) dimension. (The LRS data model, including the measure dimension, is explained in Section 7.2.)
A partitioned spatial index can be created on a partitioned table. See Section 4.1.6 for more information about partitioned spatial indexes, including benefits and restrictions.
A spatial index cannot be created on an index-organized table.
You can specify the PARALLEL keyword to cause the index creation to be parallelized. For example:
CREATE INDEX cola_spatial_idx ON cola_markets(shape) INDEXTYPE IS MDSYS.SPATIAL_INDEX PARALLEL;
For information about using the PARALLEL keyword, see the description of the parallel_clause in the section on the CREATE INDEX statement in Oracle Database SQL Reference. In addition, the following notes apply to the use of the PARALLEL keyword for creating or rebuilding (using the ALTER INDEX REBUILD statement) spatial indexes:
The PARALLEL clause is not supported for adding an index table with the ALTER INDEX statement; however, it is supported for rebuilding such an index table with the ALTER INDEX REBUILD statement. One useful scenario is to add a small second index table, and later rebuild the index table specifying the desired parameters and using parallel execution. See the parallel execution example for the ALTER INDEX REBUILD statement.
The performance cost and benefits from parallel execution for creating or rebuilding an index depend on a system's resources and load. If the system's CPUs or disk controllers are already heavily loaded, you should not specify the PARALLEL keyword.
Specifying PARALLEL for creating or rebuilding an index on tables with simple geometries, such as point data, usually results in less performance improvement than on tables with complex geometries.
Other options available for regular indexes (such as ASC and DESC) are not applicable for spatial indexes.
Spatial index creation involves creating and inserting index data, for each row in the underlying table column being spatially indexed, into a table with a prescribed format. All rows in the underlying table are processed before the insertion of index data is committed, and this requires adequate rollback segment space.
If a tablespace name is provided in the parameters clause, the user (underlying table owner) must have appropriate privileges for that tablespace.
For more information about using the layer_gtype keyword to constrain data in a layer to a geometry type, see Section 4.1.4.
The 'geodetic=FALSE' parameter is not recommended, because much of the Oracle Spatial geodetic support will be disabled. This parameter should only be used if you cannot yet reindex the data. (For more information about geodetic and non-geodetic indexes, see Section 4.1.2.)
Moreover, if you specify 'geodetic=FALSE', ensure that the tolerance value stored in the USER_SDO_GEOM_METADATA view is what would be used for Cartesian data. That is, do not use meters for the units of the tolerance value, but instead use the number of decimal places in the data followed by a 5 (for example, 0.00005). This tolerance value will be used for spatial operators. When you use spatial functions that require a tolerance value with this data, use the function format that allows you to specify a tolerance value, and specify the tolerance value in meters.
Specifying 'sdo_non_leaf_tbl=TRUE' can help query performance with large data sets if the entire R-tree table may not fit in the KEEP buffer pool. In this case, you must also cause Oracle to buffer the MDNT_...$ table in the KEEP buffer pool, for example, by using ALTER TABLE and specifying STORAGE (BUFFER_POOL KEEP). For partitioned indexes, the same sdo_non_leaf_tbl value must be used for all partitions. Any physical storage parameters, except for tablespace, are applied only to the MDRT_...$ table. The MDNT_...$ table uses only the tablespace parameter, if specified, and default values for all other physical storage parameters.
If you are creating a function-based spatial index, the number of parameters must not exceed 32. For information about using function-based spatial indexes, see Section 9.2.
To determine if a CREATE INDEX statement for a spatial index has failed, check to see if the DOMIDX_OPSTATUS column in the USER_INDEXES view is set to FAILED. This is different from the case of regular indexes, where you check to see if the STATUS column in the USER_INDEXES view is set to FAILED.
If the CREATE INDEX statement fails because of an invalid geometry, the ROWID of the failed geometry is returned in an error message along with the reason for the failure.
If the CREATE INDEX statement fails for any reason, then the DROP INDEX statement must be used to clean up the partially built index and associated metadata. If DROP INDEX does not work, add the FORCE parameter and try again.
Examples
The following example creates a spatial R-tree index named COLA_SPATIAL_IDX.
CREATE INDEX cola_spatial_idx ON cola_markets(shape) INDEXTYPE IS MDSYS.SPATIAL_INDEX;
Related Topics
Syntax
DROP INDEX [schema.]index [FORCE];
Purpose
Deletes a spatial index.
Keywords and Parameters
| Value | Description |
|---|---|
| FORCE | Causes the spatial index to be deleted from the system tables even if the index is marked in-progress or some other error condition occurs. |
Prerequisites
You must have EXECUTE privileges on the index type and its implementation type.
Usage Notes
Use DROP INDEX indexname FORCE to clean up after a failure in the CREATE INDEX statement.
Examples
The following example deletes a spatial index named OLDINDEX and forces the deletion to be performed even if the index is marked in-process or an error occurs.
DROP INDEX oldindex FORCE;
Related Topics
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